Page:Popular Science Monthly Volume 1.djvu/679

Rh The most difficult task for chemistry was the investigation of the laws of life. All that was known in regard to this was, that the living organisms of the animal and vegetable kingdoms consisted of a few elements, say three or four, which were the same in both. The difference, then, in the manifold organisms of the kingdoms must needs be quantitative; and here the first want was an accurate method of analysis. This presented a difficult problem. The first successful experiments date back as far as 1809, but the method of determining weight was as yet so complicated and wasteful of time, and required so much skill and practice, that only a few substances could be analyzed. To investigate the two organic kingdoms with greater hope of success, an easier method of analysis must be found, and here we meet the name of a man whom Germany proudly calls her own.

To Justus Liebig belongs the merit of having discovered a method by which, without loss of accuracy, the whole process was greatly simplified, and of which he himself made extensive use. As his great teacher, Gay-Lussac, had done before him, he burned the organic substance to be analyzed, in a dry glass tube with oxide of copper, condensed the resultant water in an apparatus containing a water-absorbing salt, calcium chloride, and the resultant carbonic acid was absorbed in a glass of water. This last was a glass of a peculiar shape, with a clear liquid consisting of an aqueous solution of pure caustic potash. This glass of water, which has rendered such great services to humanity, bears the name of "Liebig's potash apparatus," and appears on his pictures as interwoven with the clouds of the higher regions, thus enabling the chemist to recognize the portrait even without the signature.

By that simplified method and by the aid of the labors of his many talented students, who now adorn most of the chairs of chemistry in Europe, as well as through the geniality of the master, the immense material from which he reared the structure of organic chemistry could be collected and properly used. Agricultural chemistry may be considered a part of organic chemistry; its province is to determine the laws of the growth of plants. The year 1840 is of the same importance in the history of the world as the years 1436, 1492, and 1774, which mark the invention of printing, the discovery of America, and that of oxygen.

A report upon the application of chemistry to agriculture, which Liebig had agreed to prepare for the British Association for the Advancement of Science, convinced him of the fact that the then existing views regarding this subject consisted mainly of errors. Instead, therefore, of reporting upon agricultural chemistry, he must first create the science. He demonstrated this in the ever-memorable report which may be said to contain nearly three-fourths of the agricultural chemistry of the present day. The immense materials collected by him and his assistants were of excellent service in this work, for they had